To improve riding comfortability of a carriage, caster mechanisms have been used extensively. In certain cases, caster mechanisms are used only for improving the carriage's riding comfortability by serving as a shock absorber. In other cases, the caster mechanism is used not only for its shock absorbing characteristics, but also for its steering characteristics. Generally, in the former case, the caster mechanism is employed with the rear wheels of the carriage, and in the latter case, the caster mechanism is employed with the front wheels.
By employing caster mechanisms in the above-described manner, no problems occur when the baby carriage moves in a specific direction. Recently, the baby carriage has been modified so that a push handle can be changed easily between a forward and/or a rearward direction relative to the carriage seat. Thus, the baby carriage can be pushed while the operator faces the baby's back or while facing, the baby's front. With this arrangement, wheels located forwardly of the push handle are referred to as "front wheels", while wheels located rearwardly thereof are referred to as "rear wheels". Thus, the front wheels cannot definitely be distinguished from the rear wheels based simply on the orientation of the carriage.
When the aforementioned construction is employed for the carriage, caster mechanisms employed for both front and rear wheels must have not only an excellent shock absorbing characteristic but also an excellent steering capability. Additionally, as a practical matter, an excellent turning movement property must be exhibited for steering the wheels located forwardly of the push handle, and turning movement of the wheels located rearwardly of the push handle is inhibited for steering the wheel by a stopper unit arranged for each wheel.
To meet the foregoing requirements, a caster mechanism having a stopper mechanism added thereto has been hitherto developed, as disclosed in Japanese Kokais Nos. 63-61601 and 63-93602. However, these conventional caster mechanisms have the following drawbacks.
(1) The conventional caster mechanism has a stopper holder with an engagement groove having a stopper fitted thereto which is secured to a junction where each foot rod of the carriage is coupled to the caster mechanism. Moreover, a foremost engagement portion of the stopper formed to turn up and down on the caster side is fitted to the engagement groove of the stopper. Another stopper is arranged at the central part of the turning movement of each wheel.
As the wheels rotate, turning resistance results from contact with the ground causing each wheel to deviate from its initial position. To suppress any positional deviation of the wheels, the engagement state, e.g., the caster mechanism is operatively engaged with the foot rod, must be maintained reliably. However, since the conventional caster mechanism has the stopper mechanism positioned where resistance caused by wheel contact with the ground is concentrated, slight vibrations (positional deviation) are always generated by the wheels, resulting in the carriage having poor riding comfortability. Additionally, suppressing the positional deviation of the wheels is difficult, as a practical matter.
(2) Since the conventional caster mechanism is independently secured to the lower end of each foot rod without any operative association between the front wheels secured to the front foot rods and between the rear wheels secured to the rear foot rods, two stopper mechanisms arranged for a right-hand wheel on the rear wheel side and a left-hand wheel on the rear wheel side are separately actuated, when stopper mechanisms for a caster mechanism arranged for the two rear wheels are actuated such that the two rear wheels serve as wheels for the rear side.
(3) In the conventional baby carriage disclosed in Japanese Kokai No. 63-93602, no turning inhibition is performed to allow caster mechanisms to orient both the front and rear wheels in a specific direction. Thus, the caster mechanisms arranged for the rear wheels do not swing toward the rear side relative to the forward movement direction of the carriage when the rear wheels serve as wheels on the rear side when the baby carriage is conventionally used (see variation of the operative state from the position shown in FIG. 15 to the position shown in FIG. 16).
With this construction, the carriage cannot be folded while inoperative unless the direction of the wheel orienting toward the rear side is shifted to a direction conveniently employable for performing a carriage folding operation.